Surgical asepsis, sterilization and disinfection

PRINCIPLE OF SURGICAL ASEPSIS, STERILIZATION AND DISINFECTION

Presented byGanga Prasad Yadav

M.V.Sc., 1st SemesterVeterinary Surgery & Radiology

Common Definitions Sepsis: Presence of pathogenic microorganisms, or their

toxic products in the tissues of a patient.Asepsis: The absence of pathogenic micro-organisms in

living tissues.Aseptic technique: The clean practice used to remove or

destroy pathogens and to prevent their spread from one animal/people or place to another animal/people or place.

Antisepsis: Prevention of sepsis by the destruction or inhibition of microorganisms using an agent that may be safely applied to living tissues.

Common Definitions Antiseptic: A chemical agent that either kills pathogenic micro-

organisms, or inhibits their growth on animate (living) tissue. Example: Chlorhexidine

Disinfectant: A germicidal chemical substance that kills micro-organisms on inanimate objects. Example: glutaraldehyde.

Disinfection: Removal of micro-organisms, but not necessarily their spores and viruses found on non-living objects.

Sterilization: complete elimination of microbial viability, including vegetative forms of bacteria and spores by physical or chemical means.

Transmission of microorganisms

• Microorganisms are transmitted by

Transmission of microorganisms

Hospital Staffs EnvironmentContaminated Instruments

Sources of Contamination Sources of Contamination

Surgical personnel Non-sterile barriers:

Surgical clothing Scrub tops Surgical head cover Face masks

Sterile barriers: Gloves Surgical skin scrub

Sources of Contamination

Patient Operating theatre

environment Surgical

equipments

Principles of surgery asepsis

Followings are the principles of surgical asepsis:

1. Use only sterile items within a sterile field.2. Scrubbed personnel are gowned and gloved.3. Sterile personnel operate within a sterile filed (sterile personnel touch only sterile items or

areas, unsterile personnel touch only unsterile items or areas.

Principles of surgery asepsis

4. Sterile drapes are used to crate a sterile field.5. All items used in a sterile field must be sterile.6. All items introduced onto a sterile field should be

opened , dispensed and transferred by methods that maintain sterility and integrity.

7. A sterile field should be maintained and monitored constantly.

8. Surgical staff should be trained to recognize when they have broken technique and should know how to remedy the situation.

Levels of sterility and disinfection

• On the basis of magnitude of the risk of infection, the use of surgical instruments and equipments can be classified into three categories:

Level of Sterility and Disinfection1. Critical: Surgical Pack Instruments 2. Semicritical:

Endotracheal tube

3. Noncritical: Face masks and

Rebreathing Bags

Preparation for Surgery

• It involves:Surgeon’s preparation:1. Surgical head cover2. Mask3. Surgical shoes4. Hand scrubbing5. Hand drying6. Gowning7. Gloving

Patient preparation:1. Hair removal 2. skin preparation3. Patient draping

Scrub Solutions• Commonly used scrub

solutions are:1. Chlorhexidine - Excellent spectrum - Ocassionally sensitive

to mucous membrane.2. Povidine iodine - Excellent spectrum - Ocassionally skin

sensitive.

Wrapping Instrument Packs

Folding and Wrapping Surgical Gown

Unwrapping of Sterile Packs

Hand Scrubbing Technique

Steps in Surgical Gloving

1 2 3

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Figures: 1- 6 showing steps in surgical gloving

Sterilization and DisinfectionDestruction of all the microorganisms (bacteria,

viruses, spores) from objects (instruments, drapes, catheters, needles, blades) that come in contact with tissue or enter into the vascular space.

Disinfection: Process of destroying microorganisms except viruses and spores found in inanimate objects.

Methods of sterilization: 1. Physical sterilization 2. Chemical sterilization 3.

Gas sterilization 4. Irradiation

Physical Sterilization

most commonly used sterilization method. used dry or moist heat.1.1 Dry Heat: Mechanism of Action: Denaturation or destruction

of cellular proteins. a. Flaming:

Used to sterilized the instruments like blade, needles passing over the flame of gas burner till red hot, destroys bacteria.


b. Hot air oven: - Most common and effective method

of sterilization of metal instruments and glassware.

- A temperature of 120 C for 8 hours, ⁰140 C for 2.5 hours, 160 C for 1 hour and ⁰ ⁰180 C for 20-30 minutes is usually sufficient.⁰


1.2 Moist heat: Mechanism of action: Denaturation of major cell

constituents. a. Boiling:

Most effective method of sterilization. 2% sodium carbonate added to boiling water to

make alkalinity , that helps in destruction of microbial spore.

Uses temperature of 100 C for at least 15 minutes ⁰to sterilize syringes and needles.

Physical Sterilization.b. Autoclaving: Moist heat in the form of

saturated steam under pressure. A temperature of 121 C under ⁰

15 pounds pressure for 15 minutes.

Sharp instruments like scissors, needles and other routine instruments of a surgical pack, excluding sharp blade. Fig.: Autoclave


• Flashing : when unwrapped instruments is autoclaved for shorter period of time. Done for critical instruments. A temperature of 131 C ⁰under 30 pounds pressure per square inch for 4-7 minutes.

• In field condition, large pressure cooker is used to sterilized surgical instruments and packs under maintained pressure for 45 minutes.

Chemical or cold sterilization

Refers to immersion of instruments in tray containing disinfectant solutions such as Phenol, Alcohol (ethyl or isopropyle alcohol), Glutaraldehyde, Betapropiolactone, aldehydes (formalin), Chlorhexidine that destroys the pathogenic microorganisms on inanimate objects.

Destroy all bacteria except tubercle bacillus.


Used for sharp edged instruments like scalpel blades and hypodermic needles.

Spores and Viruses may not be destroyed so not used for critical instruments.

1. Alcohols: Mechanism of action: by Protein denaturation,

metabolic interruption and cell lysis. Isopropyl alcohol (50-70%) and ethyl alcohol (70%)

used for spot cleaning and injection site preparation.


It is corrosive to stainless steel and volatile.At lower concentration, acts as bacteriostatic

rather than bactericidal. 2. Aldehyde: Mechanism of action: By protein and nucleic

acid alkylation.


a. Formaldehyde: It is in the form of formalin, 37-40%

solution of formaldehyde and water. Capable of killing all bacteria, viruses and

spores. Extremely pungent smell, irritating to skin

and mucous membranes and has limited application as a cold sterilization agent.


40% Formalin is used in fumigator at minimum relative humidity of 70%, temperature 30-40°C to sterilize operation theatre.

180 ml of 40% formalin is used for 1000 cu ft. size of room.


Uses: Disinfection of organic wastes, hospital floors, walls. Disinfection of membranes in dialysis equipment etc.b. Glutaraldehyde: 2% solution of glutaraldehyde is used for

disinfection of lenses, dental equipments, delicate instruments or anesthetic accessories.

It is also irritating to skin and mucous membrane and odor, so well rinsed before use.


3. Chlorhexidine: An antiseptic agent available in detergent,

tincture and aqueous formulations.0.75-1% solution used for scrubbing. Widely used for preparation of surgical patients

and for surgical hand scrubs due to nonirritating property to skin.

Effective against gram negative and gram positive organisms, repeated use increases its effectiveness.


4. Quaternary ammonium compounds: It is also used in fumigation/fogging of operation theatre for 45 minutes.

Example: Microgen D-125 (a commercial product).

It is bactericidal, virucidal and fungicidal disinfectant.

15 ml of concentrate Microgen D-125mixed in 1 litre of water for disinfection every 1000 cu. Ft room in high risk areas like operation theatre, ICU, Pathology laboratory etc.

Chemical or cold sterilization5. Iodine compoundsMechanism of action: released free iodine from

carrier molecules and acts as disinfectant.1. Povidine Iodine (Betadine): Bactericidal, virucidal, fungicidal but poor

sporicidal activity. Used for cleaning of wounds, scrubbing of

hands.2. Iodophors (7.5%): Used as scrub solution for

cleaning dark colored floors and countertops.

Chemical or cold sterilization6. Chlorine compounds Mechanism of action: by chlorination and

oxidation of essential molecules.1. Hypochlorite: 2.5% sodium hypochlorite solution is used. Used for cleaning floor and countertops. Inactivated by organic debris and corrosive to

metal.


7. Phenol and its derivative:a. Phenol: 2% solution used for disinfection. Acts by disrupting the cell membranes and

precipitate cellular proteins. Bactericidal but do not affect viruses and

spores. Commonly used as cold sterilint in combination

with detergents or soaps to increase the spectrum of their activity.


b. Crysol: 0.5 – 1% of Crysol used as intestinal antiseptic.

c. Lysol: used for disinfection of non-living objects. Examples: Disinfection of floor, Bathrooms, Washbasins, organic wastes such as faeces and urine etc.

d. Chloroxylenol (dettol): 2% solution of dettol used for antiseptic for intact skin.

Gas sterilization1. Ethylene oxide gas:Effective against all types of microorganisms.Kill microorganisms by altering their normal cellular metabolism and replication through alkylation of protein, ribonucleic acids and deoxyribonucleic acid.Moisture and heat sensitive equipments can be sterilized .

Gas sterilization

• The effectiveness of ethylene oxide gas as a sterilizing agent depends on:

a. Gas concentration: 450 – 1500 mg/L. b. Temperature: usually 21- 60 C.⁰ c. Exposure time: 48 minutes to several hours. d. Humidity: 40%, necessary for lethal action

of ethylene oxide.

Gas sterilizationUsed to sterilize

Endocope Gloves Catheters Items sealed in plastic etc.

Irradiation

Radiation used for sterilization is of two types: Ionising and Non-ionising radiation.

Ionising Radiation: Uses shorter wavelengh, high intensity and high penetrating radiation to destroy microorganisms. For example: Gamma rays, X-rays.

Gamma rays have shorter wavelength with deeper penetration . Used to sterilize pre-packed items:

Surgical blades, Swabs, Catheters, Syringes Gowns Drapes Table covers etc.

Non-ionising radiation: Uses longer wavelengh having lower energy and penetration. For example: UV rays

UV rays (300-400nm wavelength) produced by mercury vapor lamp used to sterilize table surfaces, room.

References

1. Small Animal Surgery, 4th Edition by Theresa Welch Fossum.

2. Text Book of Small Animal Surgery, 3rd Edition by Douglas Slatter.

3. Ruminant Surgery by RPS Tyagi and Jit Singh.4. Fundamentals of General Veterinary Surgery by

Md. Moin Ansari.5. Veterinary Surgery Small Animal by Karen M.

Tobias and Spencer A. Johnston.

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Surgical asepsis, sterilization and disinfection

Health & Medicine